HardBiologyHigh School (9–10)GeneralEcology and Environment › Ecosystems and Food ChainsNumericalConceptual
A field of wheat stores 500 000 kJ of food energy…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A field of wheat stores kJ of food energy. People could eat the wheat, or feed it to goats and eat the goats. Using the ten per cent law, how much energy reaches people each way? Which feeds more people, and by how many times?
Need a reminder? The key ideaShow
Energy enters from the Sun; plants capture about 1% of it. About 10% of the energy passes from one trophic level to the next, and the rest is lost, mostly as heat, so energy flows one way and chains are short. Non-biodegradable chemicals build up along a chain (biological magnification), most at the top.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Wheat. One step: kJ.
Step 2. Goats. Two steps: kJ.
Step 3. Compare. .
Answer: kJ by eating the wheat, kJ by eating goats; the wheat feeds times as many people.
Discussion (0)
Log in to join the discussion.
Loading…